How draw Callipers in OpenGL

I was tasked by my teacher of cad computer graphic to do such thing. I do not know how begin. Is it beginner or advanced task? Maybe there are similar tasks. Should it be composite works with joining of primitives that were showed in printed manuals?

It should be drawn in 2d mode without animation. Would you refer for similar 2d object.
Except it I want to know where and how download library for OpenGL in Java and what is simplest way to draw objects and animation in Opengl--in c++, java or delphi-pascal (the last one is the least known by me).
For example--http://igeo.jp/tutorial/43.html--such samples ca be executed in standart java- compiler--J-grasp for example.

In general I understand that I should use Line Loop connecting the vertices. But How to draw the arc of circles or even elipses as it needed there?
I there any method to do it simply without using trigonometry?
I aslo want to know if i draw one figure (f.e. polygon) and then other one can the last one be visible and first one not visible? As there is moving part of calliper that should hide the part of scale.

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But it is probably wholly another technology. I would like to do it in opengl. Do glew and other subparts of opengl have better abilities to draw such calliper then in glut. Or maybe pascal graph is better to do it as it was first my alternative.

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Here i need to draw the filled ring. So how to do it. I have such idea. I draw bigger circle with fill (how to add just there). then i draw the empty small circle inside the first one. Am i correct especially toward the using the trygonometry for circles draw.

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Here i need to draw the filled ring. So how to do it. I have such idea. I draw bigger circle with fill (how to add just there). then i draw the empty small circle inside the first one. Am i correct especially toward the using the trygonometry for circles draw. So can the second empty fill to cover the first one